High-Q Thermally Stable Operation of a Tokamak Reactor

Thermally stable subignited operation of a tokamak reactor, sustained in operation by a feedback-controlled supplementary heating source, is discussed. One-dimensional (radial) thermal stability analyses of model transport equations, together with numerical results from a one-dimensional (1-D) transport code, are used in studying the heating of deuterium-tritium (D-T) plasmas in the thermonuclear regime. The establishment of stability depends on a number of radially nonuniform nonlinear processes whose effect is analyzed. Nonuniform heat deposition resulting from plasma core supplementary heating is found to be a thermally more stable process than bulk heating. In the presence of impurity line radiation, however, core-heated temperature profiles may collapse, contracting inward from the limiter, the result of a radiation-induced instability. The effect of nonuniform transport coefficients is also discussed. Conditions are established for the realization of a subignited high-Q (Q ? 50) toroidal reactor plasma with appreciable output power (?2000 MW thermal).     

软X光激光用多层膜反射镜的设计与性能模拟计算

介绍在研制软Ｘ光激光用多层膜反射镜中发展起来的一套设计方法。给出了这类反射镜在现阶段所研究的部分Ｘ光激光波长下的设计结果。利用波动光学迭代方法模拟计算了反射镜的性能，并讨论了膜厚控制误差、表（界）面粗糙度等对性能的影响。     

Theory Of Multilayer X-Ray Mirrors With Slowly Varying Period

Broadening of multilayer-mirror reflection band is achieved by slow variation of its period. The paper is devoted to the theory of such optical elements based on a general theory of wave propagation through a quasi-periodic medium. The calculation results are presented for the reflection coefficient of broadband mirrors in the 1 to 50 Å range. A statement of the inverse problem is also considered, namely, creation of a multilayer structure possessing the prescribed reflection coefficient.     

Beryllium-Based Multilayer Mirrors for the Soft X-Ray and Extreme Ultraviolet Wavelength Ranges

Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques - The latest experimental results of studying beryllium-containing multilayer mirrors are reviewed. The mirrors are of...     

Influence of Beryllium Barrier Layers on the Properties of Mo/Si Multilayer Mirrors

Technical Physics - The performance of multilayer Mo/Si mirrors with B4C and Be spacers near a wavelength of 13.5 nm has been studied. It has been shown that four-component Mo/Be/Si/B4C...     

Stress,Roughness and Reflectivity Properties of Sputter-Deposited B_4C Coatings for X-Ray Mirrors

Boron carbide(B_4C) coatings have high reflectivity and are widely used as mirrors for free-electron lasers in the x-ray range. However, B_4C coatings fabricated by direct-current magnetron sputtering show a strong compressive stress of about-3 GPa. By changing the argon gas pressure and nitrogen-argon gas mixing ratio, we are able to reduce the intrinsic stress to less than-1 GPa for a 50-nm-thick B_4C coating. It is found that the stress in a coating deposited at 10 m Torr is-0.69 GPa, the rms roughness of the coating surface is 0.53 nm, and the coating reflectivity is 88%, which is lower than those of coatings produced at lower working pressures. When the working gas contains 8% nitrogen and 92% argon, the B4 C coating shows not only-1.19 GPa stress but also a low rms roughness of 0.16 nm, and the measured reflectivity is 93% at the wavelength of 0.154 nm.     

Microfocus X-Ray Tubes with a Silicon Autoemission Nanocathode as an X-Ray Source

To develop nanostructures with extremely low spatial resolution (to 10 nm and below), a new concept of the use of arrays of microfocus X-ray tubes based on field emission silicon nanocathodes is proposed. A new λ-tunable microfocus source of X-ray radiation, based on a thinfilm transmission target with field emission nanocathode with tunable wavelength, is proposed. The possibility of decreasing the exposed area size to 20 nm and smaller by varying the tube blocking voltage is shown. The use of these X-ray sources opens a new way of developing maskless X-ray lithography.     

高能X射线双能成像法中的物质识别

研究了边界能量为1—10MeV的高能X射线成像系统中采用双能成像法识别物质问题. 通过研究其物理机理, 提出了一个近似线性的数学模型; 定义了物质识别灵敏度用于评价物质识别效果; 发现了双能X射线的最优能谱分布区间. 提出并验证了面向最优能谱分布区间的双能X射线能谱调制方法, 大大提高了物质识别灵敏度, 并较好解决了不易识别薄物质的问题. 建成了9MeV/6MeV交替双能成像实验样机, 获得了物质识别着色图像. 相关实验研究结果与理论研究符合得很好.     

微型X射线管出射谱特征研究及Be窗厚度确定

微型X射线管已广泛应用于现场元素分析、放射性医疗等领域,对于微型X射线管铍窗,普遍认为除保证管内真空外,应越薄越好。采用蒙特卡洛方法,模拟了从50～500 μm范围内共13个Be窗厚度的微型X射线管出射X射线谱。按照在应用中的作用,将出射X射线划分为不同能量段进行分析。通过分析谱线特征,发现Be窗厚度应依据其应用要求合理选择。因此,提出了K系特征X射线与轫致辐射强度的比值和低能射线与激发射线计数比值等参量作为评价Be窗厚度最优化的判断依据。除上述评判指标外,铍窗的厚度最优化选择还应考虑Be窗对不同能量X射线的屏蔽效果。依据模拟结果分析,原位(现场)X射线能量色散荧光分析应用中,Be窗厚度约250 μm的微型X射线管最为合适。与50 μm铍窗厚度出射射线相比,71.66%低能原级X射线被屏蔽,5~50 keV能量原级X射线仅有21.31%被屏蔽,低能射线强度占总X射线比值小于10%,且K系X射线占激发射线的比例仍保持较高的水平。因此,采用250 μm铍窗厚度的微型X射线管作为能量色散激发源,能保证探测器探测的有效信号比值较高,低能X射线对探测器的能量分辨率的影响最小,而且能量色散分析谱线的散射本底相对强度处于较低的水平,从而保证元素分析结果精准度。对于放射性治疗的应用中,则铍窗厚度越薄越好,此时,低能X射线具有较高的通量,能保证辐射剂量在治疗组织中剂量的集中。     

基于绝缘体上的硅材料的全内反射型阵列波导光栅器件的设计

设计了一种基于绝缘体上的硅材料的全内反射型阵列波导光栅解复用器年。将一全内反射波导镜引入原弯曲的波导列阵中，该波导镜具有偏振补偿的功能和缩小器件尺寸的特点。在器年数值模拟的基础上，制作了原理性器件，并获得了初步的实验结果。     

Thermally poled fused silica as a second-order autocorrelation crystal

Autocorrelation is one of the most commonly used methods for ultrashort pulses (<1 ps) characterization. Many measurement devices have been made with various nonlinear materials: second-harmonic generation in nonlinear crystals and Langmuir-Blodgett films, fluorescence in fused silica, absorption in semiconductors. We propose the use of a poled fused-silica glass as an autocorrelation crystal. This cheap and robust material can be an interesting alternative for ultrashort pulses autocorrelation.     

Study of the Interaction of Plasma with Beryllium That Is a Candidate Material for the First Wall of a Fusion Reactor

The experimental conditions for treatment of a candidate material of the first wall, beryllium, by the plasma have been determined. The plasma parameters obtained using the simulator with a plasma-beam setup during the irradiation of samples as well as the results of material studies obtained by scanning electron microscopy and energy-dispersion analysis of the beryllium surface layer have been considered.     

溶液法制备基于新型热交联主体材料OLED器件的研究

为了得到溶液法制备的高性能的OLED器件,基于咔唑和1,2,4-三氮唑基团及可热交联的苯乙烯基团,设计并合成了可热交联的主体材料VB-CzTAZ。测试结果表明,VB-CzTAZ具有很好的热稳定性(Td:323℃),把该材料溶于氯苯旋涂成膜,该膜在手套箱中190℃下发生热交联。不同溶剂的薄膜清洗实验表明,热交联后的VB-CzTAZ具有优秀的抗溶剂性。基于VB-CzTAZ溶液法制备的绿光磷光器件,最低启动电压为5.1 V,最大亮度为2 404 cd/m~2,最大电流效率为4.3 cd/A,表明该交联材料可以用于溶液法制备多层OLED器件。     

Dynamical Theory of X-Ray Diffraction in a Crystal with a Surface Grating of Another Material

Journal of Experimental and Theoretical Physics - A general theory is developed for dynamical X-ray diffraction in a crystal on the surface of which a lateral periodic structure of thin-film lines...     

Portable X-Ray Fluorescence as a Rapid Technique for Surveying Elemental Distributions in Soil

Case studies from two sites demonstrate how concentration distributions of hazardous contaminants can be rapidly measured and visualized using portable XRF (X-ray fluorescence) coupled with geostatistical interpolation tools. In this study, lead is used as an exemplar due to its well-known detrimental effect on human health through long-term exposure. A portable Thermo Scientific NITON X-ray fluorescence (XRF) instrument was used for real-time in-situ concentration measurements, which were linked to GPS coordinates of the sampling locations. A 52 point mixed sampling density survey was performed at a site near Maynooth, Co. Kildare, and a second 58 survey undertaken at Dublin City University (DCU). At Maynooth, high concentrations of Pb (above 110 mg/kg) were found close to the site where a local canal meets a road. At the DCU site, results indicate high Pb concentrations (above 160 mg/kg) near a busy main road. Geostatistical techniques were used to generate concentration prediction and critical threshold contour surfaces for both sites. Linked with GPS coordinates for each sampling location, this technology enables the distribution of multiple elements to be mapped over wide areas in a relatively short time. Supplemental materials are available for this article. Go to the publisher's online edition of Spectroscopy Letters to view the supplemental file.     

北京同步辐射装置X射线衍射实验站在材料科学研究中的应用

简述了北京同步辐射装置X射线衍射实验站的实验装置,工作性能.利用X射线衍射仪开展了非晶周期多层膜、半导体超晶格结构研究,测量了Si₃N₄材料残存应力微区分布.     

High Efficiency and Stable Organic Light-Emitting Diodes Based on Thermally Activated Delayed Fluorescence Emitter

High efficiency,stable organic light-emitting diodes(OLEDs)based on 2-pheyl-4'-carbazole-9-H-Thioxanthen-9-one-10,10-dioxide(TXO-PhCz)with different doping concentration are constructed.The stability of the encapsulated devices are investigated in detail.The devices with the 10wt% doped TXO-PhCz emitter layer(EML)show the best performance with a current efficiency of 52.1 cd/A,a power efficiency of 32.7lm/W,and an external quantum efficiency(EQE)of 17.7%.The devices based on the 10wt%-doped TXO-PhCz EML show the best operational stability with a half-life time(LT50)of 80 h,which is 8h longer than that of the reference devices based on fac-tris(2-phenylpyridinato)iridium(Ⅲ)(fr(ppy)_3).These indicate excellent stability of TXO-PhCz for redox and oxidation processes under electrical excitation and TXO-PhCz can be potentially used as the emitters for OLEDs with high efficiency and excellent stability.The high-performance device based on TXO-PhCz with high stability can be further improved by the optimization of the encapsulation technology and the development of a new host for TXO-PhCz.     

Thermally stimulated currents as a measure of degradation of zinc oxide varistors

ZnO varistor degradation phenomena was studied using thermally stimulated current (TSC) method. It is believed that asymmetrical degradation of V-I characteristics caused by DC biasing is due to charge accumulation on the reverse biased side of ZnO grain barrier. The TSCs' measuring system and cryostat apparatus used in experiment were described. The thermally stimulated currents observed in this study for varistor samples doped with different amounts of Co, due to their recovery from asymmetrical electric stress, could not be controlled by movement of Zn interstitials with activation energy 0.55 v eV, as it is widely believed, for the TSC activation energy determined in this experiment was 0.39 v eV.